1. Field of the Invention
The present invention relates to a carbon nanotube structure, a semiconductor device and a semiconductor package and, more particularly, to a semiconductor device equipped with perpendicular wiring parts such as a via or a contact and a semiconductor package equipped with a radiator.
2. Description of the Related Art
Multi-layer wiring structure has been advanced as a number of transistor elements mounted in, for example, a CMOS-type large-scale integrated circuit (LSI) increases with a reduction in a circuit scale of transistor elements and wirings in an LSI so as to satisfy the demand for improvement in high-performance, multi-functionalization and miniaturization.
Under reduction in a circuit size and multi-wiring, a wiring pitch and a cross-sectional area of a via and a contact parallel to a substrate surface are reduced increasingly, and an electric resistance of a via and the like is increased due to the reduction in the cross-sectional area. Moreover, it is known that a volume resistivity of a metal material such as Cu or the like becomes higher than a volume resistivity in a case of bulk as a cross-sectional area is reduced. Accordingly, a wiring resistance of a via and the like increases further, which results in an increase in a wiring delay due to an increase in a CR product. Thus, an effect of miniaturization may be cancelled, and the wiring delay may cause an obstacle to a high-speed transmission.
On the other hand, a carbon nanotube has a cylindrical shape made by winding a single sheet of graphite. A diameter of a carbon nanotube is about several nanometers to ten nanometers, and a length thereof is several micrometers. Therefore, an aspect ratio (length/diameter) of a carbon nanotube is about 1000, and a one-dimensional electronic behavior of the carbon nanotube due to the geometrical anisotropy has attracted attention. A carbon nanotube has a feature that a maximum current density without cut off is one million amperes per one square centimeter, which is more than 100 times larger than that of a copper wire. Additionally, a carbon nanotube has a thermal conductivity 10 times higher than that of copper. In a point of view of the electric resistance, it was reported that electrons flowing through the carbon nanotube can achieve a so-called ballistic electron transportation having no scattering phenomenon due to impurity or lattice vibration (phonon). In such a case, it is known that a resistance of a single carbon nanotube is about 6.45 kΩ.
For example, Japanese Laid-Open Patent Application No. 2003-523608 suggests a wiring structure 100 using a carbon nanotube as a via as shown in FIG. 1 that uses the electric advantage of a carbon nanotube. In the wiring structure shown in FIG. 1, carbon nanotubes 106 are caused to grow in a hole 104 extending through a non-conductive layer 103 provided between a first conductive layer 101 and a second conductive layer 102 from a catalytic layer 105 formed on the first conductive layer 101 so as to electrically connects the first conductive layer 101 and the second conductive layer 102 to each other by the carbon nanotubes 106.
However, with the wiring structure 100 shown in FIG. 1, since the carbon nanotubes 106 grow respectively from only nucleus separated with each other in the catalytic layer 105 on the first conductive layer exposed in the hole 104, there are spaces between adjacent carbon nanotubes 106, which results in a limitation in a density of the carbon nanotubes 106 in a cross section of the hole 104 parallel to the first conductive layer 101. Consequently, there is a problem in that an electric resistance cannot be sufficiently reduced relative to the cross-sectional area of the hole 104.
On the other hand, in a semiconductor package in which an LSI is mounted on a high-density mounting substrate, for example, chip size package (CSP), thermal transportation is carried out by releasing a heat generated by the LSI to an atmosphere through a heat sink made of Al or the like. Although an LSI and a heat sink are usually adhered to each other via a thermally conductive paste, a temperature of the LSI, of which amount of hear generation has been increased due to recent high-integration, is raised during an operation if the thermal resistance is not sufficiently deceased. Thus, there is a problem in that a degradation of reliability occurs such as erroneous operation or reduction in service life.